An Mw 6.1, devastating earthquake, on April 6, 2009, struck the Middle Aterno Valley (Abruzzi Apennines, Italy) due to the activation of a poorly known normal fault system. Structural analysis of the ...fault population and investigation of the relationships with the Quaternary continental deposits through integrated field and laboratory techniques were conducted in order to reconstruct the long-term, tectono-sedimentary evolution of the basin and hypothesize the size of the fault segment.
A polyphasic evolution of the Middle Aterno Valley is characterized by a conjugate, ∼E-W and ∼NS-striking fault system, during the early stage of basin development, and by a dip-slip, NW-striking fault system in a later phase.
The old conjugate fault system controlled the generation of the largest sedimentary traps in the area and is responsible for the horst and graben structures within the basin. During the Early Pleistocene the E-W and NS system reactivated with dip-slip kinematics. This gave rise to intra-basin bedrock highs and a significant syn-tectonic deposition, causing variable thickness and hiatuses of the continental infill.
Subsequently, since the end of the Early Pleistocene, with the inception of the NW-striking fault system, several NW-strands linked into longer splays and their activity migrated toward a leading segment affecting the Paganica-San Demetrio basin: the Paganica-San Demetrio fault alignment.
The findings from this work constrain and are consistent with the subsurface basin geometry inferred from previous geophysical investigations. Notably, two major elements of the ∼E-W and ∼NS-striking faults likely act as transfer to the nearby stepping active fault systems or form the boundaries, as geometric complexities, that limit the Paganica-San Demetrio fault segment overall length to 19 ± 3 km. The resulting size of the leading fault segment is coherent with the extent of the 6 April 2009 L'Aquila earthquake causative fault.
The positive match between the geologic long-term and coseismic images of the 2009 seismogenic fault highlights that the comprehensive reconstruction of the deformation history offers a unique contribution to the understanding faults seismic potential.
We provide field data of coseismic ground deformation related to the 6 April Mw 6.3 L'Aquila normal faulting earthquake. Three narrow fracture zones were mapped: Paganica‐Colle Enzano (P‐E), Mt. ...Castellano‐Mt. Stabiata (C‐S) and San Gregorio (SG). These zones define 13 km of surface ruptures that strike at 130–140°. We mapped four main types of ground deformation (free faces on bedrock fault scarps, faulting along synthetic splays and fissures with or without slip) that are probably due to the near‐surface lithology of the fault walls and the amount of slip that approached the surface coseismically. The P‐E and C‐S zones are characterized by downthrow to the SW (up to 10 cm) and opening (up to 12 cm), while the SG zone is characterized only by opening. Afterslip throw rates of 0.5–0.6 mm/day were measured along the Paganica fault, where paleoseismic evidence reveals recurring paleo‐earthquakes and post‐24.8 kyr slip‐rate ≥ 0.24 mm/yr.
We provide field data of coseismic ground deformation related to the 6 April Mw 6.3 L'Aquila normal faulting earthquake. Three narrow fracture zones were mapped: Paganica-Colle Enzano (P-E), Mt. ...Castellano-Mt. Stabiata (C-S) and San Gregorio (SG). These zones define 13 km of surface ruptures that strike at 130-140 degree . We mapped four main types of ground deformation (free faces on bedrock fault scarps, faulting along synthetic splays and fissures with or without slip) that are probably due to the near-surface lithology of the fault walls and the amount of slip that approached the surface coseismically. The P-E and C-S zones are characterized by downthrow to the SW (up to 10 cm) and opening (up to 12 cm), while the SG zone is characterized only by opening. Afterslip throw rates of 0.5-0.6 mm/day were measured along the Paganica fault, where paleoseismic evidence reveals recurring paleo-earthquakes and post-24.8 kyr slip-rate greater than or equal to 0.24 mm/yr.
We present the results of seismological and geophysical investigations performed by the “
Istituto Nazionale di Geofisica e Vulcanologia
” team operating in Amatrice village (Central Italy), in the ...emergency phases following the Mw 6.0 event of August 24th 2016, that caused severe damage in downtown and surrounding areas. Data from seven seismic stations equipped with both weak and strong motion sensors are analyzed in terms of standard spectral ratio to empirically define amplification function using a bedrock reference site. Ambient vibration spectral ratios between horizontal and vertical component of motion are also evaluated in a large number of sites, spread out in the investigated area, to recover the resonance frequency of the soft soil outcropping layers and to generalize the results obtained by earthquake data. Ambient noise vibration are also used for applying a 2D array approach based on surface waves techniques in order to define the near-surface velocity model and to verify its lateral variation. The results allows to better understand the amplification factors in the investigated area, showing spatial variation of site effects despite of the homogeneous shallow geological condition indicated by the microzonation studies available at moment of the described field campaign. The analysis reveals a diffuse amplification effect which reaches its maximum values in downtown area with a resonant frequency of about 2 Hz. The obtained results were used to integrate the microzonation studies and they can be used for urban planning and reconstruction activities.
In the literature concerning the study of emotional effect on cognition, several researches highlight the mechanisms of reasoning ability and the influence of emotions on this ability. However, up to ...now, no neuroimaging study was specifically devised to directly compare the influence on reasoning performance of visual task-unrelated with semantic task-related emotional information.
In the present functional fMRI study, we devised a novel paradigm in which emotionally negative vs. neutral visual stimuli (context) were used as primes, followed by syllogisms composed of propositions with emotionally negative vs. neutral contents respectively. Participants, in the MR scanner, were asked to assess the logical validity of the syllogisms. We have therefore manipulated the emotional state and arousal induced by the visual prime as well as the emotional interference exerted by the syllogism content.
fMRI data indicated a medial prefrontal cortex deactivation and lateral/dorsolateral prefrontal cortex activation in conditions with negative context. Furthermore, a lateral/dorsolateral prefrontal cortex modulation caused by syllogism content was observed. Finally, behavioral data confirmed the influence of emotional task-related stimuli on reasoning ability, since the performance was worse in conditions with syllogisms involving negative emotions. Therefore, on the basis of these data, we conclude that emotional states can impair the performance in reasoning tasks by means of the delayed general reactivity, whereas the emotional content of the target may require a larger amount of top-down resources to be processed.
Several methods such as paleoseismic trenching, mapping of offset geomorphic markers, and dating of scarp profiles have been used to determine slip rates of normal faults in the central Apennines. ...Combining measurements obtained with different methods remains challenging because non‐tectonic processes can introduce noise or spurious signals that are elusive to quantify, and these influence slip rate estimates. To this end, we meta‐analyzed throw measurements with associated ages collected in the central Apennines with several methods to quantify such erratic fluctuations and method‐related variances. We show that throw rates are overdispersed with respect to nominal uncertainties in throw and age; therefore, they are commonly affected by unmodeled noise processes. After comparing throw rate distributions sampling the same faults with different techniques, no clear spatio‐temporal patterns appear, but only quasi‐random noise. Assuming that field investigators sampled real tectonic features (i.e., fault scarps), we find that such erratic throw rates indicate total uncertainties are two to three times greater than the stated observation uncertainties. In this situation, a simple and robust null hypothesis is appropriate. We propose that most faults should be assumed to have uniform throw rate along their traces, except for possible tapering near unconnected ends. We also propose that models in which throw rates are time‐dependent (within the last 25 kyr) are not yet justified. Then, relying on the estimated total uncertainties, we determine the most probable long‐term fault throw rate for each active fault by combining different throw‐rate probability density functions.
Plain Language Summary
Recent advances in paleoseismology are expected to provide crucial components for seismic hazard models in the years to come. Different paleoseismological methods sample complementary features along active fault traces. Thus, the most significant progress in seismic hazard analyses using paleoseismological data will stem from advanced statistical methods comparing (and connecting) outcomes of different techniques. However, comparing alternative techniques remains problematic, given the limited number of feature measurements across the same active fault. The available data for active faults across the central Apennines, collected with diverse methods by different research groups, represents an opportunity to solve this issue due to their dense concentration. Furthermore, such data richness motivated us to carefully investigate the spatial and temporal variabilities to discriminate tectonic signals from noise. We meta‐analyzed available throw measurements (and their ages), inspected for disagreements among features, and found evidence for significant data overdispersion. Hence, we argue that better quantification of the total uncertainties is needed and that uniform throw rate (along each trace and through the last 25 kyr of geologic time) is still the most reasonable model for many scientific and urban planning purposes.
Key Points
We meta‐analyzed throw measurements for active normal faults in the central Apennines
Throw rates are overdispersed with respect to age and offset uncertainties; therefore larger uncertainties are implied
A robust null hypothesis is that faults have quasi‐constant throw rates through time and along trace except for tapering at unconnected ends
The 2016 central Apennines earthquake sequence was caused by slip on an extensional fault system and resulted in sizable coseismic surface deformation. The most evident effects occurred along the ...western slope of Mount Vettore, a geologically and morphologically complex mountain ridge. Steep topography and rheological contrasts are known to have strongly controlled the coseismic deformation pattern during a number of different earthquakes that occurred in mountainous areas worldwide. Nevertheless, so far the role of seismically induced slope failures has not been taken into account in the interpretation of the surface fractures caused by the 2016 earthquake sequence. We modeled the static and dynamic slope stability along the western flank of Mount Vettore and in the underlying Piano Grande plain. Combining the slope stability analysis with geomorphic and geological analyses, we show that the coseismic fractures are distributed along the most unstable areas of the western flank of Mount Vettore and can be partly explained by shaking‐induced mechanisms such as gravity‐driven displacement, compaction, and secondary ground failure. Conversely, in the Piano Grande plain the fracture pattern is not affected by topography or rheology contrasts, suggesting that it is positively caused by tectonic faulting. Different processes, such as gravitational and erosional‐depositional phenomena, may contribute to the exposure of fault scarps during both the coseismic and interseismic periods. Attributing the surface deformation entirely to tectonic faulting, especially in complex mountainous terrains such as the Apennines, may lead to an incorrect assessment of fault displacement and fault slip rate and hence of seismic hazard.
Key Points
We assess the topographic and rheological influences on coseismic surface deformation along Mount Vettore after the 2016 earthquake sequence
The largest coseismic offsets occurred in the most unstable zones of Mount Vettore, indicating potentially significant nontectonic deformation
The coseismic fractures in the Piano Grande were not affected by topography or rheology contrasts, supporting a tectonic origin
We investigated whether the joint inversion of geodetic and stress direction data can constrain long‐term fault slip rates in the central Apennines, and ultimately how extension is partitioned among ...fault slip and bulk lithosphere permanent strain. Geodetic velocities are collected in the fault interseismic stage with steady secular deformation; thus, long‐term estimates can be derived with a model of elastically unloading seismogenic faults within a viscously deforming lithosphere. As the average spacing of permanent Global Navigation Satellite Systems (GNSS) stations is similar to the average length of seismogenic faults (25–35 km), if not larger, we decided to merge permanent and temporary GNSS measurements, resulting in a denser geodetic data set. Given that most normal faults in the Apennines have slip rates around or below 1 mm/a, and most campaign GNSS velocities carry similar uncertainties, simple local back slip models cannot be applied. More sophisticated modeling is required to extract reasonable bulk deformation rates and long‐term fault slip rates at signal‐to‐noise ratio of order unity. Given the spatial distribution of the GNSS network, we estimated the long‐term slip rate of seven major fault systems that are in satisfactory agreement with available geological slip rates. The resulting spatial distribution of bulk deformation rates locally fits short‐term transients; in other cases, they represent the currently unclear signature of tectonic processes like upper‐crustal viscoplastic deformation and aseismic slip, or indicate missing faults in the adopted database. We conclude that the time is ripe for determining fault slip rates using geodetic and stress direction data, particularly where fault activity rates are hard to determine geologically.
Key Points
We perform a joint inversion of GNSS velocities and stress data to determine fault slip rates and bulk deformation rates in the central Apennines
Complex modeling can extract reasonable estimates of long‐term fault slip rates in satisfactory agreement with available geological estimates
Model fault slip rates may complement and constrain geological slip rates for any application in seismic hazard assessment
We performed geophysical investigations in the northwestern sector of the island of Malta to reconstruct velocity-depth models and provide shear-wave velocity profiles. We have chosen two sites, one ...located in Rabat (Malta) and another in the Golden Bay area. We used both active (seismic and electrical 2D-tomography, Multichanel Analysis of Surface Waves – MASW) and passive (2D arrays and single-station measurements using ambient noise) geophysical methods. Consistently with previous studies performed in this part of Malta, we have found that both sites are characterized by site resonance in the frequency range 1–2 Hz as an effect of the local lithostratigraphic succession that shows an impedance contrast at about 60–90 m depth. This resonance effect can have important implications on both seismic hazard as well as seismic risk evaluation of the region since the amplified frequency range coincides with the resonance frequencies typical of 5–10 storey buildings which are very diffuse in the Maltese Islands, especially after intense recent urbanization.
We also highlight the importance of performing seismic velocity measurements even at rock sites. As an example, the Golden Bay site would be classified as class “A” following the EuroCode EC8 when considering only the outcropping lithology represented by limestone rocks. Conversely the subsoil characterization provided by this study has revealed that this site falls in the EC8 class “B”, stressing the importance of direct geophysical measurements since the a-priori assignment to A-class could lead to wrong estimates in evaluating the site response.
•We performed seismic and electrical geophysical investigations in Northern Malta.•The reconstructed shear-wave velocity profile shows an impedance contrast.•The impedance contrast causes a resonance peak between 1 and 2 Hz.•This resonance effect can have important implications on the seismic hazard.•We stress the importance of performing velocity measurements even at rock sites.
In this paper we describe an advanced database for the site characterization of seismic stations, named “CRISP—Caratterizzazione della RIsposta sismica dei Siti Permanenti della rete sismica” (
...http://crisp.ingv.it
, quoted with
https://doi.org/10.13127/crisp
), designed for the Italian National Seismic Network (Rete Sismica Nazionale, RSN, operated by Istituto Nazionale di Geofisica e Vulcanologia). For each site, CRISP collects easily accessible station information, such as position, type(s) of instrumentation, instrument housing, thematic map(s) and descriptive attributes (e.g., geological characteristics, etc.), seismic analysis of recordings, and available geophysical investigations (shear-wave velocity
V
S
profile, non-linear decay curve). The archive also provides key proxy indicators derived from the available data, such as the time-averaged shear-wave velocity of the upper 30 m from the surface (V
S30
) and site and topographic classes according to the different seismic codes. Standardized procedures have been applied as motivated by the need for a homogenous set of information for all the stations. According to European Plate Observing System infrastructural objectives for the standardization of seismological data, CRISP is integrated into pre-existing INGV instrument infrastructures, shares content with the Italian Accelerometric Archive, and complies map information about the stations, as well as local geology, through web services managed by Istituto Superiore per la Protezione e la Ricerca Ambientale. The design of the CRISP archive allows the database to be continually updated and expanded whenever new data are available from the scientific community, such as the ones related to new seismic stations, map information, geophysical surveys, and seismological analyses.
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